The present invention relates to an I-beam made from engineered lumber, and having improved properties. More particularly, the present invention relates to a composite I-beam formed from a pair of parallel flanges with a web of oriented strandboard extending therebetween. At least one of the flanges is reinforced, thereby providing more desirable failure characteristics.
In residential and commercial construction, conventional solid sawn lumber joists used for floor supports (such as 2xe2x80x3xc3x9712xe2x80x3 lumber joists), usually made from spruce, fir or pine, are often being replaced by I-beams. An I-beam is a structural member having upper and lower flanges corresponding to the top and bottom horizontal portions of the xe2x80x9cIxe2x80x9d and what is referred to as a web therebetween. Of course, the strength of the I-beam depends on the materials of construction, where, for instance, a steel I-beam is structurally stronger (albeit much heavier) than a wood I-beam, as well as the dimensions of the component parts, where, for instance, an I-beam having a tall web is generally stronger than an I-beam with a short web (assuming the same thickness of web and size of the flanges). That said, wood I-beams can be stronger and lighter, as well as less expensive, than similar sizes of solid sawn lumber.
Although steel I-beams may be most desirable in terms of strength, the weight and cost of steel I-beams make them prohibitive. Although wood I-beams are far more desirable than steel I-beams in terms of weight and cost, for applications such as residential construction, the behavior of the wood I-beam in case of fire is an important consideration. More specifically, regardless of the strength and other characteristics of a wood I-beam, without having fire endurance and related properties equivalent to or better than solid sawn lumber joists, wood I-beam are of limited practicality in most applications. Included in the desirable characteristics is time-to-failure and failure mode (i.e., whether the failure is catastrophic, or sudden, or whether there is bowing/deflection and other effects usually observed with solid sawn lumber) of solid sawn lumber in a fire.
As noted, a wood I-beam, also often referred to as a composite I-beam, typically has two flanges, an upper flange (i.e., the flange which is that nearest the floor of the building in which the I-beam is used) and a lower flange (i.e., the flange sitting furthest away from (and below) the floor of the building in which the I-beam is used), with a web therebetween. The web is often, but not always, formed of plywood, oriented strandboard (xe2x80x9cOSBxe2x80x9d) or other form of engineered lumber, and inserted into the flanges by means of a groove routed into the flanges. Engineered lumber refers to a lumber product made from natural wood, but that has been processed or engineered such that it is no longer in its original form. For instance, a laminate of strips of wood (from which the flanges of a wood I-beam are often formed), commonly referred to as laminated veneer lumber (xe2x80x9cLVLxe2x80x9d), would be considered engineered lumber. Likewise, OSB is another form of engineered lumber, formed by bonding wood particles with a resin system to form a relatively continuous sheet or web.
What is desirable, therefore, is a wood I-beam comprising two flanges with a generally continuous web arranged therebetween, where the I-beam has a time-to-failure and/or failure mode at least equivalent to solid sawn lumber.
It is an object of the present invention to provide an I-beam useful as a floor joist for residential or commercial construction.
It is another object of the present invention to provide an I-beam lighter in weight and less expensive to manufacture than a steel I-beam of corresponding dimensions.
It is still another object of the present invention to provide an I-beam stronger and lighter in weight than an equivalent length of solid sawn lumber joists.
It is a further object of the present invention to provide an I-beam having time-to-failure and failure mode at least equivalent to solid sawn lumber joists.
These objects and others that will become apparent to the artisan upon review of the following description can be accomplished by providing a composite I-beam having a first flange and a second flange, with a generally continuous web extending between the flanges. At least one of the flanges includes a reinforcing layer of a supporting material either thereon or therein. In particular, at least one of the flanges of the I-beam (and possibly both of the flanges) is a laminated flange having a plurality of wood members adhesively joined together into a generally rectangular cross-section, wherein a reinforcing layer of a supporting material is disposed between at least two of the plurality of wood members. The reinforcing layer is preferably a sheet of fibrous material having a thickness of no more than about 0.030 inch and can be a sheet of fiberglass, aramid fibers, para-aramid fibers, polymetaphenylene diamine fibers, polytetrafluoroethylene fibers, high modulus polyethylene, graphite fibers, carbon fibers, or mixtures thereof. The reinforcing layer of supporting material can also be disposed between more than two of the plurality of wood members in one or both of the laminated flanges or in the groove routed into one or both of the flanges.
In another embodiment of the claimed invention, at least one (and possibly both) of the flanges of the I-beam is made from a length of solid sawn lumber having a generally rectangular cross-section having two major and two minor surfaces, wherein a reinforcing layer of a supporting material is disposed on at least one of the major surfaces of the flange, and possible both of the major surfaces of the flange, or in the groove routed into the flanges. Again, the reinforcing layer can be a sheet or bundle of fibrous material having a thickness of no more than about 0.030 inch, formed from a sheet of fiberglass, aramid fibers, para-aramid fibers, polymetaphenylene diamine fibers, polytetrafluoroethylene fibers, high modulus polyethylene, graphite fibers, carbon fibers, or mixtures thereof.